Moses 7:13 describes the battle led by Enoch:
And so great was the faith of Enoch that he led the people of God, and their enemies came to battle against them; and he spake the word of the Lord, and the earth trembled, and the mountains fled, even according to his command; and the rivers of water were turned out of their course; and the roar of the lions was heard out of the wilderness; and all nations feared greatly, so powerful was the word of Enoch, and so great was the power of the language which God had given him.
Why would Joseph Smith say that the roars of lions were heard? Notably, the Book of Giants also mentions the roaring of beasts after the battle:
the roar of the wild beasts has come and they bellowed a feral roar.
Where would Joseph Smith have gotten this curious idea?